Connector crimping die set



July 23, 1963 D. R. ZELL ET AL 3,098,517

CONNECTOR CR 3,098,517 CONNECTOR CRIMPING DEE SET Dale R. Zell,Harrisburg, and John A. Zimmerman, In,

Hershey, Fa, assignors to Incorporated, Harrisburg, Pa.

Filed Mar. 9, 1960, Ser. No. 13,778 6 Claims. (Cl. 153-4) This inventionrelates to crimping devices for electrical terminals and connectors.

One known form of crimping die set for electrical connectors comprises afirst crimping die having a recess therein with convergent surfaces anda second crimping die or anvil movable relatively into the recess. Uponmovement of the anvil into the crimping die, the terminal is compressedand crimped onto a wire positioned in the terminal. The crimps formed bythis type of die set are classified as confined crimps for the reasonthat the connector ferrule is intended to be completelycircumferentially confined during at least the final stages of crimping.With this arrangement, it is apparent that since the surfaces of therecess converge towards each other, a gap will be left between thelateral edges of the anvil and the surfaces of the die during at leastthe initial portion of thecrimping operation and in fact, it is commonto design such die sets so this gap is closed only near the very end ofthe crimping operation.

Now, in virtually all connector crimping operations, the flow stress ofthe metal of the connector (i.e. the stress required to cause plasticdeformation) is, and must be, exceeded and the metal of the connectortends to be extraded in those areas where it is not confined againstextrusion. Thus, the metal of the ferrule may, and frequently does, fiowaxially so that the ferrule is lengthened as well as intended and/ orflattened by the crimping operation. This axial flow is an expectedphenomenon and is not necessarily regarded as being harmful. However, ifa gap is left between the lateral edges of the anvil or second die andthe surface of the recessed crimping die as explained above, the metalof the ferrule may also flow through this gap to produce extrudedflanges on the ferrule after crimping. It should also be mentioned thatwith some connector ferrules having relatively thin walls, the ferrulewall may be sheared by the lateral edges of the anvil before it iscompletely confined within the recess by the crimping anvil.

Both of these results are undesirable in a confined type of crimp andare avoided if possible. According to one known method of avoiding theseeffects, the crimping die and anvil are made to very precise dimensionaltolerances and the connector ferrule is also carefully matcheddimensionally to the particular die set being used for crimping to avoidextrusion. In accordance with this method, the dies and the ferrule areformed in a manner such that the flow stress (or shear stress) of themetal of the ferrule is not imposed upon the ferrule until it has beencompletely ciroumferentially confined by closure of the gap between thecrimping dies so that no undesirable radial extrusion or shearing cantake place. However, if the crimping die set departs from the precisedimensional tolerances required, or if the ferrule of the connector isnot carefully matched to the crimping die set, conditions exist whichmight give rise to the extrusion or the shearing of the ferrule asexplained above.

It would thus be desirable to avoid the foregoing effects without thenecessity of adhering to extremely close tolerances in the die set andthe connector. Furthermore, it would be desirable to form the die set ina manner such that it could accept and crimp different sizes of ferruleswithout the extrusion and shearing effects described above so that asingle die set might be used for different sizes of connectors.

3,098,517. Patented July 23, 1963 It is accordingly an object of theinstant invention to provide an improved die set for crimping electricalconnectors. It is a further object to provide a die set having arecesesd crimping die and a crimping anvil which anvil adapts itselfduring crimping to the dimensions of the die. It is a further object toprovide a crimping anvil which is cooperable with a recesesd crimpingdie in a manner such that during the initial stages of a crimpingoperation, and before the flow stress or shear stress of the ferrule isimposed upon the ferrule, the lateral edges of the anvil engage theopposed surfaces of the recess in the die to prevent extrusion orshearing of the ferrule.

These and other objects are achieved in one preferred form of theinvention in which the anvil is medially slotted so that its upperportions are divided into two separate fingers. In one embodiment, thesefingers are so formed that they diverge and are slightly flexibletowards each other and towards the medial plane of the slot. As theanvil is moved relatively into the recess in the crimping die, thelateral edges of these fingers come into contact with the opposedconvergent surfaces of the recess in the die and are cammed and flexedtowards each other whereby they are maintained in close engagement withthe surfaces of the crimping die. Advantageously, the crimping anvil isso dimensioned relative to the width of the recess in the die that theedges of the fingers come into contact with the sides of the recessbefore substantial crimping of the terminal begins so that during mostof the crimping operation, the fingers are resiliently pressed againstthe opposed surfaces of the die recess. With this arrangement, no gapremains bet-ween the edges of the anvil and the surfaces of the dieduring crimping so that extrusion of the metal of the ferrule orshearing of the ferrule is prevented.

In the drawing:

FIGURE 1 is a frontal view of a die set in accordance with a preferredembodiment of the invention;

FIGURES 2 and 3 are views showing the crimping operation with theembodiment of FIGURE 1;

FIGURES 4, 5 and 6 are views similar to FIGURES l, 2 and 3 but showingan alternative embodiment;

FIGURE 7 is a frontal view of a conventional prior art type of die setintended to perform the same type of crimping operation as theembodiments of FIGURES 1 and 4;

FIGURE 8 is a view showing the dies of FIGURE 7 in the closed conditionat the end of a crimping operation;

FIGURE 9 is a sectional view of a crimped connection formed inaccordance with the prior art teachings and by a die set of the typeshown in FIGURES 7 and 8 and illustrating the extrusion effectssometimes obtained; and

FIGURE 10 is a view of a crimped connection showing the shearing effectwhich is sometimes obtained with prior art die sets.

The problem to which the instant invention is addressed can be bestappreciated from FIGURES 7-10 wherein the reference numeral 2 denotes acrimping die having a recess with convergent surfaces 6 which curvetowards each other and merge with each other as shown at 8. The anvilblock 20' has a crimping anvil 22 extending therefrom which provides anarcuate upper surface 24 adapted to receive the ferrule 10 of anelectrical connector into which a conductor 12 has been inserted.Ideally, the anvil 22 should be of a width such that extrusion of themetal of the ferrule 10 into the gap between the lateral edges 26 of theanvil and the surfaces 6 of the recess cannot take place. In actuality,if the recess in the crimping die is slightly oversized or the anvil isslightly undersized, or if the ferrule 10' of the connector is slightlyoversized, a substantial gap 23 (FIGURE 8) will remain. Upon crimping,as shown in FIGURE 8, the metal of the ferrule will be extrudeddownwardly through this gap and form flanges as shown at 25, FIGURE 9.Such extrusion of the metal will take place readily with soft metal suchas copper but has been observed with brass and harder connectorferrules. FIGURE illustrates a condition which also arises with dies ofthe type shown in FIGURES 7 and 8 Where a gap is left between the edgesof the anvil and the opposed surfaces of the crimping die. Crimpedconnections as shown in FIGURE 10 are sometimes obtained if the ferrulehas a relatively thin wall rather than a comparatively thick wall andthe ferrule is sheared at 27 by the lateral edges of the anvil duringthe initial stages of crimping. The results shown in FIGURES 9 and 10are undesirable for a number of reasons. For example, in both instancesan undesirable and useless projection on the ferrule is produced whichmay interfere with the usage of the crimped connection in someenvironments where space limitations are of importance such as where theconnector is of the pin and socket type and is adapted to be used in adielectric connector block having a plurality of relatively closelyspaced openings for the connectors. Furthermore, the conditions shown inFIGURES 9 and 10 result in a weakening of the connector ferrule. Aspreviously pointed out, these conditions can be avoided by precise andaccurate dimensioning of the crimping die set and careful selection ofthe size of the terminal being crimped. However, this solution to theproblem is not always satisfactory because of the high manufacturingcost involved for precisely dimensioned dies and the inability of thetool manufacturer to control the sizes of terminals which will becrimped with the tool in use by the ultimate user.

FIGURE 1 shows one embodiment of the instant invention in which thecondition shown in FIGURES 9 and 10 are avoided. In this embodiment theupper crimping die 2 is formed as is the die 2 of FIGURE 7. The lowerdie block 4 has an anvil 13 extending therefrom which is mediallyslotted as shown at 14 to form a pair of fingers 15 which in thisembodiment diverge slightly from each other and from the center line ofthe die set. To achieve this divergence, the anvil projection 13 may beinitially formed (e.g. by milling, investment casting or any othersuitable method) with divergent sidewalls 17 so that after the slot 14is cut the fingers will diverge from each other. Alternatively, theanvil projection 13 may have straight sidewalls as formed and, after theslot 14 has been cut, the two fingers 15 may be permanently deformed bybeing spread apart. In the disclosed embodiment the upper surfaces 16 ofthe fingers are of arcuate form and provide edges 18 extending along thesides of the die at the tops of the sidewalls.

In the embodiment of FIGURE 1, the width of the upper portion of theanvil projection 13 (the distance between the edges 18 of the fingers)should be such that when the anvil is moved relatively into the recessof the crimping die, these edges will come into contact with theconvergent surfaces 6 prior to the imposition of any substantialcompressive force on the ferrule 10 of the termihad. In use, when thecrimping die and anvil move relatively towards each other and the edges18 engage the convergent surfaces 6, the fingers 15 are cammedrelatively towards each other to permit the die parts to move together.During the interval of crimping between the position of the parts shownin FIGURE 2 and the position shown in FIGURE 3, the edges 18- of theanvil are always pressed against the sidewalls so that no gap is left(as in FIGURE 8) for extrusion of the ferrule of the connector. By thesame token, the danger of shearing the wall of the ferrule as shown inFIGURE 10 is avoided since the outside surface of the ferrule issupported around substantially its entire periphery.

It will be noted that some slight extrusion of the ferrule into the slot14 of the anvil may take place during crimping as shown in FIGURE 3 andcause the formation of an axial-1y extending rib 'on the externalsurface of the ferrule. However, it has been found that the amount ofextrusion into this slot will be limited by the fact that the tendencyof each side of the ferrule to ex-trude into this slot counteracts thetendency of the other side to extrude and the stresses imposed upon theferrule in this area are thus circurnferentially transmitted across thetop of the slot. Obviously, slot 15 should be relatively narrow in orderto reduce the tendency towards extrusion since the wider this slot ismade the less resistance will be offered towards extrusion.

FIGURE 4 shows an alternative embodiment of the invention in whichcorresponding parts with reference to the embodiment of FIGURE 1 areidentified by similar reference numerals but differentiated by primemarks. In this embodiment the anvil projection 13" has straight andpanailel, rather than divergent sidewalls so that when the ferrule iscompressed between the surfaces 16 of the fin gers and the portion 8 ofthe recess, the transmitted compressive forces urge the two fingersapart and against the sidewalls 6 of the crimping die. It will beapparent that the anvil 13" of the embodiment of FIGURE 4 wouldordinarily be movable almost to the end of the recess in the crimpingdie '2. but that the fingers are spread by the terminal. This spreadingof the fingers is a result of the fact that the forces transmittedthrough the ferrule are transmitted normally with respect to thesurfaces 16' of the anvil.

It will be noted that in the embodiment of FIGURES 13 the wire 12 isshown as having an insulating sheath 1-1 thereover while in theembodiment of FIGURES 4-6 the wire is shown as being uninsul ated. Bothembodirments can be used with either insulated or uninsulated wires andthe showing of the drawing is not intended as being limiting of theinvention.

Bot-h embodiments of the invention rely upon the principle of deformingthe crimping anvil to bring the sides or edges thereof into engagementwith the opposed surfaces of the crimping die thereby to confine theterminal during the crimping operation. It has been found in practicethat in the case of die sets adapted to crimp relatively smallterminals, the fingers of the anvil can be formed with sufii'cientresilience and flexibility to permit the movement as shown in FIGURES l6of the drawing. It is feasible, where the die set is intended for largersize terminals, to form two parallel slats to form three fingers, thecenter finger being immobile during crimping While the outer fingerswould deflect to adapt the anvil to the die as with the disclosedembodiments. Aiterna tively, it is feasible to form the anvil in twoseparate parts normally spring biased apart but movable relativelytowards each other as in FIGURE 1 or normally biased towards each otherby a separate spring but movable apart when an axial load is imposed asin FIGURE 4.

A principal advantage of the invention is that anvils and crimping diescan be manufactured, panticularly in relatively small sizes, without thenecessity of rigidly adhering to extremely precise, or close,dimensional tolerances and/or imposing equally precise tolerances on theterminals crirnped by the tool. When the teachings of the presentinvention are followed, the manufacturing tolerances can be relaxedsubstantially and the advantages of complete peripheral confinement ofthe terminal will still be obtained.

Changes in construction will occur to those skilled in the art andvarious apparently different modifications and embodiments may be madewithout departing from the scope of the invention. The matter set forthin the foregoing description and accompanying drawings is offered by wayof illustration only. The actual scope of the invention is intended tobe defined in the following claims when viewed in their properperspective against the rior art.

We claim: r

1. A crimping die set for crimping electrical terminals onto the ends ofwires comprising, a crimping die and a crimping anvil, said die having arecess with opposed convergent surfaces for reception of an uncrimpedterminal, the depth of said recess being substantially greater than thediameter :of the uncrimped terminal, said anvil being adapted to entersaid die recess to crimp said terminal by a confined crimp, said anvilhaving a relatively deep slot extending thereacross parallel to the axisthereof, said slot dividing said ranvil into two fingers, said fingersbeing movable by flexure with respect to each other and into engagementwith said convergent surfaces during crimping whereby said terminal issubstantially completely circumferentially confined against radialextrusion.

2. Apparatus as set forth in claim 1 wherein said fingers divergetowards their ends and the normal distance separating the lateral edgesof said fingers is greater than the width of said recess at the locationin said recess where a terminal is initially compressed by said die setwhereby, said fingers engage said convergent surfaces and are cammedtowards each other to substantially complete ly circumferentiallyconfine said terminal.

3. Apparatus as set forth in claim 1 wherein said fingers are movable byflexure away from each other and away from said slot upon application offorces against their terminal engaging surfaces whereby, upon initialcompression of said terminal between said crimping die and said anvil,said fingers are flexed towards, and engage, said convergent surfiacesthereby to substantially completely circumferentially confine saidterminal.

4. A crimping die set for crimping electrical connectors onto the endsof wires with a confined crimp comprising, a crimping die having arecess therein with opposed convergent surfaces, the depth of saidrecess being substantially greater than the diameter of the uncrimpedterminal, a crimping anvil mounted for movement into said recess, saidanvil being fiormed of a pair of divergent fingers, said fingers havingside edges engageable with said convergent surfaces of said recess uponmovement of said anvil into said recess whereby said fingers are cammedtowards each other and are maintained against said convergent surfaces,and said terminal is substantially completely circumferentially confinedagainst radial extrusion during crimping.

5. Means for crimping electrical connectors onto the ends of wires by aconfined crimp comprising, a crimping die and a crimping anvil, saidcrimping die having a recess with convergent surfaces, the depth of saidrecess being substantially greater than the diameter of the uncrimpedterminal, said anvil being relatively movable into said recess tocompress and crimp a terminal, a relatively deep slot in said anvilextending axially thereacross, said slot dividing said anvil into twosections which are re siliently movable by flexure relatively towardsand away from each other, the normal distance between the extremelateral edges of said two sections being greater than the distancebetween said convergent surfaces at the location in said recess where aterminal is initially compressed between said crimping die and saidanvil whereby, upon movement of said anvil into said recess, saidlateral edges engage said surfaces concomitantly with initialcompression of said terminal, and during further movement of said anvil,said sections are cammed relatively towards each other while beingresiliently maintained in engagement with said surfaces whereby saidterminal is substantially completely circumferentially confined againstradial extrusion.

-6. A crimping die set for crimping electrical connectors onto the endsof wires with a confined crimp comprising, a crimping die having arecess therein with opposed convergent surfaces, the depth of saidrecess being substantially greater than the diameter 10f the uncrimpedterminal, a crimping anvil mounted for movement into said recess, saidanvil being formed of a pair of fingers movable by flexure away fromeach other upon application of forces against their terminal engagingsurfaces, the normal distance between the extreme lateral edges of saidfingers being less than the distance between said convergent surfaces atthe location in said recess where a terminal is initially compressed ina crimping operation between said crimping die and said anvil whereby,upon movement of said anvil into said recess, said fingers are spreadapart by forces transmitted through the terminal being cn'mped at theoutset of crimping thereby to form with said convergent surfaces asubstantially complete circumferential enclosure for said terminalwhereby radial extrusion of said terminal during crimping is avoided.

References Cited in the file of this patent UNITED STATES PATENTS365,251 Gardner et al June 21, 1887 2,438,023 Sirp Mar. 16, 19482,592,276 Haclcbarth Apr. 8, 1952 2,837,135 Demler June 3, 1958

1. A CRIMPING DIE SET FOR CRIMPING ELECTRICAL TERMINALS ONTO THE ENDS OFWIRES COMPRISING, A CRIMPING DIE AND A CRIMPING ANVIL, SAID DIE HAVING ARECESS WITH OPPOSED CONVERGENT SURFACES FOR RECEPTION OF AN UNCRIMPEDTERMINAL, THE DEPTH OF SAID RECESS BEING SUBSTANTIALLY GREATER THAN THEDIAMETER OF THE UNCRIMPED TERMINAL, SAID ANVIL BEING ADAPTED TO ENTERSAID DIE RECESS TO CRIMP SAID TERMINAL BY A CONFINED CRIMP, SAID ANVILHAVING A RELATIVELY DEEP SLOT EXTENDING THEREACROSS PARALLEL TO THE AXISTHEREOF, SAID SLOT DIVIDING SAID ANVIL INTO TWO FINGERS, SAID FINGERSBEING MOVABLE BY FLEXURE WITH RESPECT TO EACH OTHER AND INTO ENGAGEMENTWITH SAID CONVERGENT SURFACES DURING CRIMPING WHEREBY SAID TERMINAL ISSUBSTANTIALLY COMPLETELY CIRCUMFERENTIALLY CONFINED AGAINST RADIALEXTRUSION.